Coarsening the reference vs. the detection?

[.Scott]

According to phys.org:

In a new study published in Physical Review Letters, physicists Hyunseok Jeong and Youngrong Lim at Seoul National University in Seoul, Korea, and M. S. Kim at Imperial College London in the UK, have proposed an explanation.

They explain that a complete measurement process is composed of two parts: one part is to set and control a measurement reference (such as timing or angle), and the other is the final detection. All of the previous studies have focused on coarsening the resolution of the final detection.

Here, the physicists looked at both parts of the measurement process and found that their coarsening leads to completely different outcomes. Their main result is that coarsening the measurement reference always forces the quantum-to-classical transition, while coarsening the final detection does not.

This is very unclear to me.

How would one coarsen a reference angle? It seems to me it would be very difficult to set an angle without being able to check it later to determine exactly what angle you ended up setting.

On the other hand, coarsening the detection would seem to mean using a detector with a large aperture so that when a detection is made, it will not be precisely where the particle was detected. Would that be a good example?

 

[DrChinese]

The full article:

http://arxiv.org/abs/1307.3746

"We investigate the role of inefficiency in quantum measurements in the quantum-to-classical transition, and consistently observe the quantum-to-classical transition by coarsening the references of the measurements (e.g. when and where to measure). Our result suggests that the definition of measurement precision in quantum theory should include the degree of the observer's ability to precisely control the measurement references. "

 

[DrChinese]

As long as you don't think you have gone past the limits of the uncertainty principle, this would make sense.

 

[.Scott]

The full article:
http://arxiv.org/abs/1307.3746

I don't have access to the full original paper.

"... Our result suggests that the definition of measurement precision in quantum theory should include the degree of the observer's ability to precisely control the measurement references."

This is perhaps the part that I least follow. It would seem to me that regardless of how well the reference was controlled, it would remain in the same state after the measurement so that it could be determined exactly what measurement had been made.

For example, let's say your control a an angle is a relatively fuzzy plus/minus 3 degrees. So you set to a target of 15 degrees, make the fuzzy measurement, and get the classical result. Then you go back and measure the angle and discover it is precisely 14.321 degrees. Why would you result be any different than if you were aiming for 14.321 degrees to begin with.

Obviously I am not interpreting their statement correctly. I'm hoping someone can explain the correct interpretation.

 

[.Scott]

I didn;t look at that page closely enough. There is a link there to the full paper:
http://arxiv.org/pdf/1307.3746v2.pdf

I've scanned through that paper. It doesn't look like I'm going to have my answer until I read it pretty closely.